The invention relates to an artificial receptor capable of binding specific biological moieties, and more particularly, to methods of using same for typing ligands, determining binding domains in proteins, targeted delivery and release of drug molecules, and gaining electrical control over biological processes.
Electrostatic interactions underlie the basis of various biological processes involving the recognition and binding of macromolecules such as DNA, RNA, proteins and carbohydrates to each other. For example, alien macromolecules are identified through molecular recognition between an antibody molecule and the intruding molecule, generally denoted antigen. Likewise, ligands such as hormones bind to their cellular receptors and thus activate cellular responses.
The mammalian immune system offers a vast repertoire of antibody molecules capable of binding selectively an immense number of molecules presented to the body by invading pathogens such as bacteria, viruses, and parasites. Albeit the fact that this repertoire evolved to target mostly bio-molecules, it may potentially contain selective binders to other targets or be expanded to include such binders. Indeed, injection of cholesterol and 1,4-dinitrobenzen (Perl-Treves, D., et al., 1996; Bromberg, R., et al., 1998) microscopic crystals as well as C60 conjugated to bovine thyroglobulin to mice (Braden, B. C. et al. 2000) have resulted in generation of antibodies against these materials by the immune system of the injected animal.
Characterization of the domain structures involved in protein-protein interactions such as those between ligands and receptors or antibodies and antigens is crucial for gaining control over such biological processes. Such a characterization can be performed using site directed mutagenesis, in which targeted mutations are introduced into DNA sequences encoding specific proteins (e.g., a receptor) and the effect of the mutation is tested in vitro following the expression of the mutated DNA in suitable cells in the presence of a test molecule (e.g., a labeled ligand). Another approach for characterizing binding domain in a protein is crystallography of a purified protein in the presence of a labeled ligand. Such experiments often results in determination of the amino acids involved in binding the ligand. However, while the first approach is limited by the specific mutations introduced, the latter approach is relatively expensive due to the need of substantial purification steps of the protein of interest.
Most drug molecules are administered using oral or intravenous administration which often result in various unwanted side effects. Such effects result from the interaction of the drug molecule with tissues or organs not intended to be treated by the drug. To overcome such limitations, various targeted drug delivery approaches were developed. These include, viral infection, temperature-sensitive liposome formulations (Viglianti B L, et al., Magn Reson Med. 2004, 51: 1153-62), magnetoliposomes (Kullberg M. et al., Med. Hypotheses. 2005, 64: 468-70), ultrasound-mediated microbubbles (Tsutsui J M, et al., Cardiovasc Ultrasound. 2004, 2: 23) and the like.
There is thus a widely recognized need for, and it would be highly advantageous to have, methods of gaining control over biological processes, characterizing domain structures for protein-protein interactions and efficient targeted drug delivery devoid of the above limitations.